Question

упростите выражение sin21 cos25 - cos21 sin25 / cos38 cos34 + sin38 sin34

Answer 1

sinacosb-cosasinb=sin(a-b)
cosacosb+sinasinb=cos(a-b)
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sin(21-25)/cos(38-34)=sin(-4)/cos4=-sin4/cos4=-tg4